Au-Ag合金纳米粒子制备及其表面增强拉曼光谱研究

首先采用柠檬酸钠法制得Au-Ag合金纳米种子, 然后采用盐酸羟胺生长法得到不同组成的Au-Ag合金纳米粒子. 在其UV-Vis光谱中只观察到一个位于单金属银和金之间的等离子体共振峰, 表明Au-Ag合金纳米粒子已经形成. TEM结果表明, 合金纳米粒子的粒径约为60 nm, 且颜色均一, 没有明显的核壳结构. 用苯硫酚(TP)作为探针分子研究了合金纳米粒子的表面增强拉曼光谱(SERS). 结果表明, SERS强度与合金纳米粒子的组成和尺寸有关. 当纳米粒子粒径一定时, 除Au25Ag75外, 随着金的增加SERS强度增强. Au25Ag75的粒径比Ag小, 导致SERS强度比Ag低. Au50Ag50和Au75Ag25加入TP分子后, 其聚集方式与Au相似, 等离子体共振峰逐渐靠近1064 nm, 金含量较高时, TP的SERS归于聚集体的等离子体共振增强的贡献.

Preparation and Surface Enhanced Raman Spectroscopic Studies on Au-Ag Alloy Nanoparticles

Au-Ag alloy nanoparticles with different molar ratios were prepared by using sodium citrate as the reducer,and the size was increased via the NH_2OH\5HCl-growth method.One plasmon band between that of monometallic Ag and Au observed in their UV-Vis spectra indicated the formation of Au-Ag alloy nanoparticles.TEM results showed diameters about 60 nm and homogeneous color of the alloy nanoparticles without clear core-shell contrast.By using thiophenol as the probe molecules,SERS studies were performed.The results indicated the SERS effect was dependent on the composition and size of the alloy nanoparticles.At the certain sizes of nanoparticles,the SERS intensities were increased gradually with the increase of gold content except Au_(25)Ag_(75).As Au_(25)Ag_(75) were smaller than Ag,the size effect made the SERS intensity of Au_(25)Ag_(75) lower.While aggregating way of Au_(50)Ag_(50) and Au_(75)Ag_(25) after adding TP molecules were gradually close to Au,and the surface plasma resonance of aggregates approached to 1 064 nm,so SERS of TP at higher Au content was controlled by surface plasma resonance enhancement of aggregates.